1. Field of the Invention
The present invention relates generally to a structure of a rotor of an alternating current (AC) generator or motor, and more particularly, to a structure for mounting permanent magnets in the rotor to prevent leakage of magnetic flux from between facing side faces of adjacent claw-shaped magnetic poles.
2. Description of the Background Art
There exist conventionally known techniques for increasing output of a rotating electric machine whose rotor includes a pair of intermeshed pole core bodies having claw-shaped magnetic poles. One of such techniques is to fit permanent magnets in gaps between one claw-shaped magnetic pole and the next which are arranged along a circumferential direction of the rotor in order to reduce leakage of magnetic flux through the gaps between the adjacent claw-shaped magnetic poles for increasing output of a rotating electric machine.
Japanese Patent Application Publication No. 2001-86715 discloses an arrangement for fixing permanent magnets in gaps between adjacent claw-shaped magnetic poles for preventing magnetic flux leakage through the gaps. According to the Publication, the permanent magnet fitted on each side of every claw-shaped magnetic pole is fixed thereto by means of a reinforcing member having a generally M-shaped or C-shaped cross section in such a manner that the reinforcing member embraces the permanent magnet. With this arrangement, the permanent magnets embraced by respective reinforcing members can be fixed to the claw-shaped magnetic poles in a reliable fashion. Also, the reinforcing members sustain centrifugal force exerted on the permanent magnets as well as flutter-producing force acting on the claw-shaped magnetic poles, so that the reinforcing members serve to mitigate adverse influence of these forces on the permanent magnets. Additionally, each of the reinforcing members has a magnet-retaining structure which prevents the permanent magnets from coming off the reinforcing member in either a basal-end or extreme-end direction thereof.
The claw-shaped magnetic poles are shaped such that an outer surface of each claw-shaped magnetic pole has a generally trapezoidal shape narrowing from a basal end toward an extreme end, and side faces of each claw-shaped magnetic pole also narrow from the basal end toward the extreme end.
This conventional arrangement has a problem that, if the reinforcing members having the aforementioned magnet-retaining structure are to be installed after the permanent magnets have been fitted on both sides of each claw-shaped magnetic pole, it is difficult to install the reinforcing members, because the magnet-retaining structure of each reinforcing member interferes with the permanent magnets. Another problem of the conventional arrangement is that, if the reinforcing members are to be installed after the permanent magnets have been affixed to each reinforcing member, gaps are likely to be created between the permanent magnets and the side faces of each claw-shaped magnetic pole, thereby causing leakage of magnetic flux through the gaps and eventual performance degradation of the rotating electric machine.